Hi, for a study I'm doing I need to get a view about the IO of the freight railroads transportation sector in Chile. Let me give you a bit of background. I'm just concern about the Railroad public company EFE (Empresa de Ferrocarriles del Estado) network, located in the center southen part of the country. There are two private freight operators which pay access charges established in two separate but equal acces contracts, which are regulated by EFE, a part of the contract) that follow the typical natural monopoly regulated price structure (a fix charge for right of using the rails, a variable chage in terms of kilometers of network usage and a variable charge in terms of volumes transported (TKBC, gross tons kilometers). In euros of 2014 per 1.000 gross tonnes, Chile's vharges (4 euros) was the fifth more expensive access charge compared to a large pool of european countries, and since then access charges has gone up and are currently in 5 euros per 1.000 gross tonnes. Although there are only two freight operators (yet it is open to more but have had no entrance since 2000, EFE operates only in the passenger segment) it is a very contestable market (trucks competition is ample and benefited from indirect government support). How would you be modelling a market like that? Bilateral monopoly with different bargainning powers? Natural Monopoly waters down and duopoly waters up (they curretly compete only in a fraction of the network but potentially all over)? or local monopolies water up? To add more complexity one of the freigth operators is vertically integrated with one important maritime port, and prevents competition from the other around that area. What reference you advice me? I need something simple, it is a study that is aimed at providing policy insight based on understanding the sector's IO, not on publishing an academic paper. Thank you in advance.